Various types of medical devices employ a needle for piercing the skin of a patient for diagnostic or therapeutic purposes. One such device is an intravenous catheter insertion device for positioning a needle mounted catheter into a patient's blood vessel. Once the catheter is properly positioned, the catheter insertion device is withdrawn leaving the catheter in place in the blood vessel. Handling of such medical devices after the needle is withdrawn from the patient can result in transmission of various pathogens, most notably human immune virus (HIV), due to an inadvertent needle stick to medical personnel.
Since the mid-1980s, concern over the risk of accidental needle stick injuries has spawned a number of design approaches for safety needle devices. Such devices can be broadly categorized as either sliding sheath needle devices, wherein a physical barrier is positioned over the needle tip after use or as devices with needle retraction, wherein the exposed portion of the needle is retracted into the device after use. The latter category of needle retraction devices can be further subdivided into manual and semi-automatic retraction devices. Manual retraction devices, as exemplified by U.S. Pat. Nos. 4,026,287 to Haller, 4,592,744 to Jagger, 4,808,169 to Haber et al. and 5,067,490 to Haber, require the user to pull or slide a needle-connected mechanism rearwardly to retract the needle into the device. In semi-automatic needle retraction devices, a biasing member, such as a spring, may be employed to push or pull the needle into the device in response to activation by the user of a release mechanism. Such devices are exemplified by U.S. Pat. Nos. 4,813,426 to Haber et al. and 5,125,414 to Dysarz.
U.S. Pat. No. 4,747,831 of Kulli and U.S. Pat. No. 4,900,307 of Kulli show respective catheter insertion devices and syringes with semi-automatic needle retraction. The retraction mechanism shown in the last-mentioned two patents are disclosed to be actuatable by the user upon depression of a release button after the catheter is removed from the insertion device or the needle is removed from the patient.
Of the aforementioned prior art devices which have semi-automatic needle retraction mechanisms, all require a needle structure having an enlarged head or rim extending radially outwardly from the axis of the needle to provide a block or enlarged surface on the needle. The needle is biased toward retraction by a spring which is compressed against the block. Generally, the block, and, hence the needle, is retrained against retraction by a latching arrangement or latch mechanism. In such devices, failure of the latch mechanism or accidental activation would cause inability to retract the needle or premature retraction of the needle occurs. Hence, it would be desirable to provide an automatic needle retraction mechanism in which the latch mechanism operates in a simple fail safe manner.
In addition, the prior art semi-automatic devices require manual actuation by the operator. In many situations, such as an emergency situation, the operator is distracted or rushed so that the manual step necessary to effectuate retraction is not performed, either intentionally or unintentionally. In such instances, the used needle remains exposed, creating a risk of an inadvertent needle stick. Therefore, it would be desirable to provide an automatic needle retraction mechanism in which needle retraction is effectuated by normal operation of inserting the catheter into the patient, without the need to perform a separate manual step.